This has triggered the perennial hope that Rubio is building an “exit ramp”–an excuse for him to bail on his own Gang of 8 bill when his new border security amendment is turned down. That hope is almost certainly false. If you employ the paradigm that Rubio is cagily trying to negotiate a tough comprehensive deal and is ready to walk (and effectively kill it) at any moment, there is some discordant data (like why did he pick veteran legalization advocate Cesar Conda as his chief of staff, and why didn’t he walk earlier in the process when he was stiffed on at least some of his demands, why did he sign off on a weak deal in the first place). If your paradigm is that Rubio’s mission is to do whatever is necessary to sell an amnesty-based reform to conservatives–including lying to Mark Levin about the powers of the Gang’s toothless “border commission”–there is no discordant data.

So what’s Rubio’s scam this time? Conn Carroll and Mark Krikorian seem to have almost solved the mystery: The original Gang of 8 bill makes legalization (into Registered Provisional Immigrant, or RPI, status) hinge only on the production of a “border security plan” by DHS. That’s an easy enough thing for DHS to produce, if they don’t have it stored on a thumb drive already. Making it a prerequisite to legalization and pretending that’s a big deal is “an insult to our intelligence,” says Idaho Sen. Jim Risch. Rubio seems to have in mind that this paperwork plan will be somehow written by Congress, not by the Department of Homeland Security. Then the President–initially, President Obama–can enforce, defer, waive, modify and otherwise fail to implement the plan as he or she sees fit.

Would the change in the plan’s authorship be a real impediment to the Gang of 8’s instant legalization? I suppose it might be if it required another vote of both chambers months down the road. But not if it’s set up under some sort of legislative-veto arrangement–where it goes into effect unless both houses vote to stop it. Or if it is somehow mandated, but not required as a prerequisite for RPI-style legalization–e.g. missing the deadline or otherwise blowing off the mandate has no consequence. Or if it’s added before initial passage of “comprehensive” legislation–perhaps by downloading DHS’s thumb-drive plan into the text of the Gang of 8 bill. I would expect Rubio and his staff to explore all three options.

Under this theory, if Rubio gets his way, he’ll have another fig leaf scared conservatives can use to rationalize their support of legalization (and he will have stroked Sen. Rand Paul, perhaps winning his vote). If he loses, he’ll stay on the bill anyway.

P.S.: Q-What would be an actually effective border-security amendment? A.: Switching the bill from “Amnesty First” to “Enforcement First.” You could still guarantee legalization, but only after specific enforcement steps (e.g. near-universal use of E-Verify employment checks; a finished border fence) had actually been taken, and had survived court challenges. As Charles Krauthammer noted, “There would be overwhelming bipartisan pressure to get enforcement done as quickly as possible.” But the White House and Democratic leadership will never agree to such an amendment–they’d rather have no bill and make that an issue in the 2014 elections. Good outcome! If Dems win those elections, they win–they will be able to go ahead and pass their bill. If they lose, the legalization-before-security fever might finally break.